Elimination of condenser and accumulator in a hydrocarbon conversion process



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J. V. JOLLY ELIMINATION OF CONDENSER AND ACCUMULATOR 1N A HYnRocARBoN CONVERSION PRocEss Filed sept. 23, 194s oct. 28, 1952 INVENTOR. J. V. JOLLY A T TORNEYS Patented Oct. 28, 1952 ELIMINATION OF CONDENSER AND ACCU- MULATOR IN A HYDROCARBON CONVER- SION PROCESS John v. Jouy, Phiuips, Tex., assignor to Phillips Petroleum Company, a corporation of Delaware Application September 23, 1948, Serial No. 50,776

9 Claims. (Cl. 260-683.4)

This invention relates to the distillation of mixtures of hydrogen fluoride and hydrocarbons. In a specific embodiment the invention relates to the recovery of hydrogen iiuoride from admixture with hydrocarbonrmaterial containing lowboiling parain hydrocarbons. The invention in a specific modification relates to the operation of an azeotropic fractionation wherein a low-boil-f ing paran-hydrogen fluoride azeotrope is recovered overhead with the production of a hydrogen uoride-free bottom product. This application is a continuation-in-part of my copending application Serial No. 667,813, iiled May 7, 1946, now abandoned.

Hydrogen iiuoride has recently come into prominence as a very important catalyst for numerous organic reactions. For example, it is used as a catalyst in the conversion of hydrocarbons by alkylation, isomerization, reconstruction, cracking, cyclization and/ or aromatization. It is also used as a reactant in the production of alkyl fluorides. Liquid hydrogen iiuoride has also been found useful as a rening agent or selective solvent in the removal of certain impurities from saturated hydrocarbons. In such reactions hydrogen fluoride is used alone, or is promoted with a small amount of boron triuoride, such as 0.1 to per cent by weight of the total catalyst.

Perhaps the most important industrial process at the present time involving the use of hy-V drogen fluoride is the alkylation of low-boiling parainic hydrocarbons, particularly isobutane, with alkylating agents,V particularly 10W-boiling clefins such as ethylene, propylene, butylenes and amylenes, to form normally liquid highoctane-number parains suitable for use in motor and aviation fuels. In such alkylation processes the reactants are intimately contacted, generally in the liquid phase, with concentrated ,hydroiiuoric acid, and reaction effluents are passed to a settling zone wherein a liquid hydrocarbonrich phase and a lliquid acid-rich phase are separated. Most of the acid phase is recycled to the reaction and a portion thereof may be subjected to purification, as `by distillation for the removal of water and acid-soluble oils, before being reintroduced as a catalyst into the process. The hydrocarbon phase is ordinarily introduced into a, fractionating tower provided with kettle heating and reux cooling, from which tower an low-boiling parain reactant, such as isobutane, is maintained in the alkylation reaction mixture, and some propane is usually also present, there is an adequate amount of low-boiling paraflin hydrocarbons in the feed to the azeotrope tower to allow complete separation of hydrogen fluoride overhead. The overhead product is subjected to separate cooling and condensation and the resulting condensate is passed to a settling zone or overhead fractionris recovered comprising all the hydrogen fluoride together with at least sufcient low-boiling hydrocarbons to form azeotropes therewith. Inasmuch as a large excess of the accumulator for separation of acid phase and hyf drocarbon phase. The acid phase is returned to the reaction, while the hydrocarbon phase is pumped to the top of the azeotrope tower to provide liquid reflux. A large volume of light hydrocarbons must thus be continually condensed by a condenser inserted in the overhead line from the fractionator. The accumulator and pump required for this operation are of course subject to corrosion by the acid.

`It is an object of this invention to provide an improved process for the distillation of hydrogen fluoride-containing mixtures.

Another object is to recover hydrogen fluoride from admixture with hydrocarbons.

A further object is to improve the operation of a fractionation system in which a minimum- :boiling azeotropic mixture of hydrogen uoride with low-boiling paraiiinic hydrocarbon material is produced in an overhead product.

Another object is to reduce the amount of cooling required in such a system. f

Another object is to reduce the pressure in such a system.

A further object is to reduce the equipment needed for such a system.

A yet further object is to provide such a system in which the amount of equipment in contact with acid is reduced.

Another object is to increase the capacity of a fractionator.

Still another object is to recover a hydrocarbon fraction substantially free of hydrogen uoride from a mixture containing low-boiling hydrocarbons and hydrogen fluoride.

A further object is to provide an improved method for recovering hydrogen uoridecatalyst for re-use in a reaction Zone, and to recover hydrocarbon material free from hydrogen iiuoride, in a process for the conversion of hydrocarbons, particularly in an alkylation process.

Other objects and advantages of the invention will be apparent, to one skilled in the art, from the accompanying disclosure and description. r

I have now discovered an improved manner of carrying out fractionations of the nature described. By employing the principles of my invention the complete recovery of hydrogen luoride, and any accompanying promoter, such as boron trifluoride, from the overhead fraction is possible without the necessity of providing the conventional condenser and accumulator, while still producing the desired HF-free bottom product. In-this` improved manner of operating the azeotropic distillation, the cooling ordinarily provided in the top of the azeotrope tower may be'f entirely dispensed with. Noris it-necessaryto provide an arrangement for -separate condensation and recovery of overhead product. In addition to the savings in equipment, which is an important item at the present time',`theamount of equipment in contact with acid, and hence `certain amount of light hydrocarbons and smaller `amountsof heavier...hydrocarbons continuously circulate, this-.circuit comprising the settler, top of the .azeo tower, and back to the settler, and also comprising the reaction zone when the vaporoustmixture'is' introduced into the reaction zone." `H'y'dro'fluric acid dissolved in the hydrosubject to corrosion, is reduced. .A given traery tionator is also enabled to handle a larger load., that is, produce more bottom product of agiven purity. f

The improved operation-iszobtainedsin :a -very simple manner by `introducing the liquid fhydrocarbon phase, from which acid has been settled but which still contains. dissolved hydrolluoric acid, as feed to ythe fractionaton `preferably at the top of the fractionator .rather than 4at an intermediate point vas is conventional, andrremoving overhead vaporsrandreturning thesame to a point in the system ahead Vof the V`fractionv ator. In one embodimentiof mysinventiong'this overhead vaporous mixture is preferably passed directly to the acid settler, withoutlcondensation thereof. In another embodimentfof my invention, this uncondensed vaporous mixture is returned directly to the reaction Zoneandadmiired with liquid in, or `passing to, the reaction zone. The liquid feed to the fractionator is normally obtainable at substantially'atmospheric temperatures, i. e. r to 115 F., and since the fractionator is readily and usually operated at elevatedv temperatures, the feed itself provides all the cooling that is necessary within the fractionator. Even when the feed is at somewhat elevated temperatures, the fractionator is easily operated at sufiiciently higher temperature that the feed vacts as reflux. In some cases, in fact, the feed "is heated somewhat before introduction into the fractionator. It will accordingly be Aseen that the liquid feed containing 4dissolved hydrogen fluoride as well as low-boiling unreacted hydrocarbons and higher-boiling alkylate acts as refluxing medium for the azeotrope tower. Essentially,` therefore, the azeotrope tower operates as a stripping column. The overhead vapors carrying the hydrogen fluoride are returned directly to some liquid in the system ahead of the fractionatoig such as the acid settler or the reaction Zone.

When the overhead vapors are passed into the liquid, either in the acid settler or in the reaction zone, the vapors are condensed bythe cooling effect of the liquid. Since the overhead vapors in liquid volume per unit of time, is generally no more than about' one tenth the volume of the liquid stream passing'from the settler to the azeotrope fractionator, and is not much Vwarmer than the liquid with which it is admixed, the increase in temperature of the liquid to which the vapor is added is very small and has no adverse effect upon the operation of the system. When the uncondensed vapor is introduced into the reaction zone, any tendency toward a temperature rise is quickly offset byremoval of heat by the cooling meansL which is usually present.

Such an operation Vas rthis lis impossiblein ordinary `fractional distillations because of con- ,carbonvphasepasses once through this circuit and upon returning to the settler in the overhead condensate does not redissolve in the hydrocarbon phase, which is alreadyr saturated with HF, but settles-'zout andiis recovered with the acid phase. The total-hydrocarbon portion of the reactor eiuent, `except .that small .part which is dissolved ingthe acid phase, .passesinto the fractionator and out `as kettle' product. The net effectiis that the'hyclrocarbon phase from the acid settler is stripped only .off dissolved hydrogen uoride. By the'prac'ticefof :my'inventionnot only are considerable equipment and cooling costs avoided but antextremely smooth operation vof the fractionatorfis obtained. `Thisis due in part to the fact that` Vonly'rone stream Yneed be Vcontrolled as' it enters thefractionator,-as-well Yas to the elimination of the condensation lof ithe. overhead by the conventional'condenser. 'By operating the fractionator asV anstripper without a `condenser in accordance with the invention, the capacity of thefractionator isrincreased, and it may be operated at atlowerfpressure, or vat higher temperatures, which in any case allows greater throughput.

Although it is preferable to introduce the feed into fthe azeotrope tower at 'the top thereof to eliminate 'the rectifying section of the'tower, a portion of the feed'may vbe introduced into an intermediate point of the tower and another portion of the feed :introduced above the intermediate feedpoint as a liquid reflux, if desire-d. Furthermore, cooling coils or like external cooling'means maybe positioned in the upper portion of the tower or column to aid in cooling fluid in the upper portion Vof the column without departing from the scope of this' invention. When external cooling of the upper portion of the column is practiced, Aall of the 'feed may be introduced at an intermediate point inthe column, which method of opera-tion results in the formation of a rectifying section-in the upper portion of the column anda stripping section in the lower portionof'the column.

In any of the above described methods for operation of the azeotrope tower, the overhead vapors fromv the tower are at a temperature approximatelythe sameas the temperature of the .liquid `feed to `-the tower. These overhead vapors are passed directly into the liquid which eventually comprises the feed to the column, preferably directly into either the acid settler, which, because of the equally large volumes of both' liquid acid and :liquid hydrocarbons at a temperature usually below about V" F., condenses all the condensible'gases of the overhead fraction, or intothereactionzone which is usuallysupplied with cooling. means ato remove heat of exotherinic reaction, and lalso is at a temperature'of 75 to 115-125 F. The'uncondensible gases from the overhead fraction of the efuent itself are vented `from the acid` settler in the conventional manner.

The invention may perhaps be more adequately understood by reference to the accompanying drawing and description thereof. The drawing represents somewhat diagrammatically one preferred arrangement of apparatus elements,`

and ow of materials therethrough, in which the process of the invention may be practiced. While the elements essential'to an understanding of the invention are shown in the drawing, it will be appreciated thatvarious auxiliary pieces of equipment may be provided by one skilled in the art. It will also be appreciated that various modications and omissions maybe made without departing'from the spirit and scope of the invention.

In the drawing a reaction zone is represented diagrammatically by the'rectan'gle l0. In a' preferred operation this reactor is used in carrying out the alkylation of a low-boiling paraiin, preferably isobutane, with one or more low-boiling olens, such as a mixture of butenes. The isoparain may be introduced by line l2 while the olen is introduced by line I4. VlVIake-up liquid hydrogen uoride catalyst is introduced through line l5. The bulk cf the catalyst is recycled to the reactor from the bottom of settling tank I8 via lines 20 and 22. In some cases it is'desirable to incorporate a minor amount of boron fluoride with the liquid hydrogen iiuoride as disclosed in the copending application of Frey, Serial No..V

than alkylation may be carried out in reactor I0, such as isomerization and cyclization. For' example, the isomerization of saturated hydrocarbons in the presence of hydrogenuoride as a catalyst may be carried'out in reactor lll.' Furthermore, a combination of I-IF-catalyzed alkylation and isomerization reactions may be eiectedf It will be effluents from any of such processes or others I able hydrocarbons,

in reactor Il? in one or more stages. appreciated that my invention may be applied to treatment of hydrocarbon'materialsin'which an v eiiluent stream containing hydrogen fluoride and low-boiling hydrocarbons is obtaire'd'f'I'he apcomprise one or more reaction zones and l may in paratus comprising reactor ID may accordingly be varied to suit the particularprocess andwillf addition comprise" much auxiliary apparatus' whichl need notA be'shown or "discu'ssedheren detail. Y i

`Considering the casev in which is 5b11`tar'1e fis" alkylated with butylenes in reactor l0, liquid con? centrated hydrouoric acid and liquid hydrocar bon reactants under pressure, are agitated toreaction takes place.V The'emulsion -is vigorouslow concentration and thus discourage polymerization and permit a maximum of alkylation. A several-fold molar excess, at least, of isobutane over olefin is maintained to minimize realkylation of primary alkylate. Normal paraiiins act as dilwith tracesof lighter gases. A reaction' tempera.

ture of '75 to 115 F. gives good results and can be maintained by water cooling to take up exothermic heatof reaction; refrigeration is not necessary. Reaction time is less than one hour, and 'ordinarily' 10 to 15 minutes is adequate. With continued use the acid acquires acid-soluble organic contaminants which are removed by distillation; the titratable vacidity of the catalyst phase is usually maintained at 85 to 90 per cent.

Eiiluents from the reactor Zone lli contain unconverted low-boiling hydrocarbons including propane and a largeexcess of isobutane, together With higher-boiling paraflinic hydrocarbons produced by alkylation reaction and hydrogen iiuoride catalyst. ously withdrawn via line Zd'and passed to settling tank I8, wherein a' phase separation is readily obtained. In case the conversion carried out in reactor I0 is at a temperature above that allowYl ing separation of the eluents into the liquid phases, suitablecooling vmeans (not shown) may be provided in line 24 to effect the desired condensation and bring the mixture to the preferred temperature range for liquid phase separation. such as the range of 75 to'llf F. just mentioned. An acid-rich phase is withdrawn from settler I8 via line 20, `as heretofore mentioned, and returned by pump 2l to the reactor. A portion of this acid phase is usually withdrawn via line 2S and passed to purification means not shown, after which it is reintroduced along with make-up acid through line ltv'. From settling tank i8 the upper hydrocarbon-rich phase, which contains small amounts of hydrogen iluoride dissolved therein is passed vialine 3 0 into surge tank 32; -Small amounts of undissolved acid may drop out in Vtank 32 and be recovere ol through line 3A. Pop-01T lines 29 and 3l are provided at the tops'of tanks i3 and 32, respectivelyzfior release o f small amounts of light-gases which may accumulate therein. Vent gases from linesS and 3! may be passed throughan absorber to remove any 'hydrogen iiuoride contained therein as well as valu- A conventional method for removing` any hydrogen fluoride from the vent gases comprises contactingthe gases inthe alosorber with an oleiinic absorption liquidand the subsequent separation and recovery of hydrogen iiuoride from the absorption liquid. rlhe operationmay beperformedby ashort absorption column 33 built directly. ontop osurge tank 3 2, with direct communicationbetween. the two, so that Aeases ,passup .frpmthe upper portion of tank 32 int@ absorber. iiand. absorption liquid flwsfdown from .absorber 3 3 into the liquid in surge tanl32. Aliquid,oleiin-containingstream is introduced to the top of absorber 33- through lineS; this may be a portion of the sanieolefn streamwhich vis Aintroducf-d .through line M, or maybe heavier olens whichwill also react with isobutane to'produc'e a suitableallszylatef4 The ol`efi-ri's"`1"eactV with free rto form corresponding 1y circulated to distribute 'the oinnreataitin 75m-Kyi uuorides, andra resulting Iiq'uid mixture of 'Such effluents are continu# hydrocarbons and alkyl fluoride flows; down-` Vapors .f of;

by means of pump 38 and passed via line 46: and/or line il! and/or line 43 into fractionatorl 42, but is preferably introduced upon the top tray of the fra'ctionator. This `liquid feed is or dinar-ily obtainedfrom surge tank 32 at substantially atmospheric temperature, oronly'slightly above such as 75 to 11E-125 F. andneed not be further cooled before being introduced into Vtower lili. In fact, in order to increase the capacity of the fractionator, the feed stream maybe heatedsomewhat by heater '39.

In azeotrope tower A2 ,a continuous fractionationis carried out whereby-all of ther dissolved hydrogen-humide Vis strippedfrom the feed and withdrawn in the overhead product via line 44 usually along with at least sufficient propane, isobutane, and/or other light hydrocarbons to form an azeotropic mixture therewith. Propane and lighter gases may comprise afsubstantial proportion of the light hydrocarbon material taken off in line '44, the-remainder being isobutane and heavier; including only a very small amount of vaporized alkylate. The uncondensed low-boiling fraction in line lil may be passed to settling tank I8, or through line l5 to surge tank 32, or both. The overhead vapor in line a4 mayV be passed, into, or bubbledl through, the liquid ineither tank I 8 or tank 32, but preferably tank I8, and is substantially all condensed except for non-condensible vapors which are through lines 29 or 3 I, or through absorber 33. If

desired, any part or all of the uncondensed overhead vapor from fractional distillation tower 42 may be passed directly into reactor I0 through lines 44 and 46 or, alternatively, through lines 4l, 48, and/or 48, into one or more of lines I, I6, and/or L2, respectively. In either case, this uncondensed vaporous mixture, is introduced into and rapidly mixed with a large amount of liquid, and is condensed by and/or absorbed by said liquid, and is again eventually passed to settling tank I8. When passed into a large body of liquid, as in tank I8 or tank 32, thevaporshould be passed into thebottom ofthe liquidso that any bubbles whichV are formed have an adequate chance to be absorbed, or have condensable material absorbed therefrom. As previously mentioned.. the .temperatureof this vaporous mixture will not `be much. higher than the tempera ture of the liquid to which it is added.

From the bottom of fractionator 42 a liquid stream is passed by means of pump 50 through line 52 v,into reboilermeans .54, wherein. sufficient l drawnthrough line58. This product comprises the normally-liquid*alkylate as .wellas inert hy.-

In the arrangement shown.. heated..4

r vented kazeotrope tower d2.

drocarbonsz-` and? excess., isobutane, and corresponde essentially to Vthe hydrocarbon content `of thereactor eilluents except for'that dissolved in,

the acid phase in settler I8. The hydrogen 11u0- rideefree kettle product isppassed to further fractionation means (notshown) for the recovery and recycle of 'isobutane through line I2, and recovery of the Adesired alkylate. Ordinarily this kettle product is subjected to a conventional de- `iluorination treatment prior to such fractionation.

As an .example of theactualoperation of an alkylationplant in accordance with my invention,.the following data are presented. It will be appreciatedV that these data are merely illustrative and. areA not to.V be construed as unduly limitingV the invention. A combined hydrocarbon feedincluding freshreactants plus` recycled iso.- butano is passed into the reactors at 95 F.- at a rate of.960 barrels per hour. The temperature of thisfeed may upon occasion vary from about to about 110 F., and the quantity may range from. 80G to 1000 barrels per hour, depending upon availability of feed stocks. Recycle, regenerated, and makeup acid enters at similar ternperatures and similar'rates (about 1040 barrels per hour), so that `about a 1:1 volume ratio oi hydrocarbon to acid is used. When the conventional condenser and accumulator is used on the overhead from the azeotrope tower and the resulting condensate is recycled, such as to settler I8, the temperature of the contents of the settler I3 is about 95 F; and the pressure is about 115 pounds per square inch gage (1GO to 120 range).

f `About 1040 barrels per hour of acid are separated in settler I8 and recycled to the reactor. About 1160 barrels per hour of hydrocarbon material are passed from settler I8 to surge tank 32 and, after removal of a small quantity of acid from the hydrocarbon material therein, the hydrooarbon stream is'passed through line 35 and heater 3S; wherein it is raised to a temperature of about to about 155 F., in this case about 148 F., at which temperature it enters the top tray of This hydrocarbon stream may vary from about 1000 to about 1200` barrels per hour with the previously mentioned range of feed rates. Column d2 is a 7 foot diameter, 20 plate fractionator, and is operated with a kettle temperature of about 190 F. (180 to 200 F. ordinary range) at about 175 pounds per square inch gage pressure V(rangingfrom to 190 pounds), and an Aoverhead vapor temperature of about 148"F, (145 to 155 F. range). The overhead vapors'upon `a liquid basis amount to about 150 to 200 barrels per hour of which 2 tol about 15 barrelsiperhour is hydrogen fluoride. In the specific operation hereindescribed, about 200 barrels per hour overheadfis produced of which .about .4 "barrelsis vhydrogen fluoride.

The kettle product of. about 1000 barrels per hour is sub stantially free from hydrogen fluoride. When the same operation is conducted without the use of the conventional condenser and accumulatoron; the overhead from theV azeotrope tower,

'51.9 ation represents an appreciable overload on the column in comparison with design and ordinarily used throughput rates. However, the practice of the present invention is an important factor in enabling the column to handle this load and still produce a hydrogen fluoride-free kettle product.

In a variant of the procedure just described, the overhead vapors 'from tower 42 are passed through lines 4 and M into the liquid, recycledf hydroiluoric acid flowing through lines 22 and I6 into reactor Ill. With other conditions the .same as just discussed, land with theV same amount of cooling watersupplied to heat-exchangers in reactor l0, the temperature of the;`

reaction mixture in reactor Hl is 2 to 7 higher, and the temperature of the contents of the acid settler I8 are, again, from about 100', to 105 F.

It will be appreciated, by those skilled in the art, that various modifications of my inventionmay be practiced, in the lightl of the foregoing teachings and disclosure, without departing from the spirit of the disclosure or from the scope of thev claims.

prises subjecting such amixture to conditions.

forming a liquid hydrogenl fluoride-rich 'phase anda liquid hydrocarbon-rich phase in a separating zone, withdrawing said liquid hydrogen fluoride-rich phase, passing said liquid hydrocarbon-rich phase containing dissolved hydrogen fluoride into a fractional distillation Zone, and separating from said fractional distillation zone a vaporous low-boiling fraction containing a lowboiling paraflin hydrocarbon and hydrogen fluoride, the improvement which comprises passing said vaporous fraction directly from said distillation zone into said liquid hydrocarbon-rich phase without intermediate condensation of the vaporous fraction in such a manner that vapors bubble into the liquid and condense therein, and separating also from said fractional distillation zone a liquid higher-boiling hydrocarbon fraction substantially free from hydrogen fluoride.

2. In a process for separating a hydrocarbon fraction substantially free from hydrogen uoride from a mixture containing low-boiling paraffin hydrocarbons and hydrogen fluoride, which comprises subjecting such a mixture to conditions forming a liquid hydrogen uoriderich phase and a liquid hydrocarbon-rich phase in a separating zone, withdrawing said liquid hydrogen uoride-rich phase, passing said liquid hydrocarbon-rich phase containing dissolved hydrogen fluoride into a fractional distillation zone, and separating from said fractional distillation zone a vaporous low-boiling fraction containing a low-boiling paraffin hydrocarbon and hydrogen uoride, the improvement which comprises passing said vaporous fraction directly from said distillation zone to said separating zone without intermediate condensation of the vaporous fraction in such a manner that vapors bubble into the liquid in said separating zone and condense therein, and separating also from said fractional distillation zone a liquid higher-boiling hydrocarbon fraction substantially free from hydrogen fluoride.

3. In a process for reacting paraiiin hydrocarbons in the presence of hydrogen fluoride, the improvement which comprises passing anueiiluent 1, directly from a reaction zone,v inwhic'h a lowboiling paraffin is. reacted' in the presence of a catalyst comprisinghydrogen fluoride,'tov va separating zone under conditions such that Va liquid hydrogen fluoride-rich phasefseparates from a LA liquid hydrocarbon-rich phase, returning atleast afportion of said liquid hydrogen fluoride-rich phaser back to said reaction Zone, passing said liquid hydrocarbon-rich phase containing 'dissolved hydrogenfluoride to a'high point in a fractional distillation zone as feed therefor, strip- `.ping from said feed in said fractional distillationzone a vaporous low-boiling fraction containing hydrogen fluoride and a low-boiling parain, passing said vaporous low-boiling fraction directly from said fractional distillation zone into` the liquid in said separatingzone without intermediate condensation thereof, and recovering a liquid high-boiling fraction from said distillation zone substantially free from hydrogen sA fluoride.

4. In a process for the alkylation of isobutane withv a low-boiling olefin in the presence of hydrogen fluoride as the catalyst comprising passing an efliuent from 'said alkylation to a separa- -tion Zone in which a liquid hydrogen fluoriderich phase anda liquid hydrocarbon-rich phase' are formed; recycling atleast a lportion of said hydrogen fluoride-rich phase to said alkylation as the catalyst therefor and passing said hydro- .lrcarbon-richfphaseA` containing dissolved hydrogen uoride'tov a fractional distillation Zone in which a vaporous overhead fraction containing hydrogen uoride and isobutane in about the azeotropic ratio and a liquid bottom fraction substantially free from hydrogen fluoride are recovered, the improvement which comprises passing said vaporous overhead fraction from said fractional distillation zone directly into the liq- `uid in said separation zone without intermediate condensation of said vaporous overhead fraction. under conditions such that at least a majorfportion of said vaporous overhead fraction is cooled, condensed and separated into a hydrogen fluc-` rde-rich phase and a hydrocarbon-rich phase.

5. In a process for reacting a low-boiling paraffin hydrocarbon in the presence ofa catalysty comprising hydrogen fluoride and subsequently distilling in a distillationV zone` a mixture of hydrogen fluoride and low-boiling 4parafn hydrocarbons from a liquid hydrocarbon mixture containing dissolved hydrogen fluoride charged to said distillation Zone from" said reaction, the improvement which comprises separating directly from said fractional distillation zone a vaporous low-boiling fraction containing a low-boiling paraifn hydrocarbon and hydrogen fluoride, passing said vaporous fraction without intermediate condensation thereof directly into a liquid hydrocarbon-hydrogen fluoride mixvand therein separating a liquid hydrogen fluoride-rich phase and a liquid hydrocarbon-rich phase, andpassing said liquid hydrocarbon-rich phase containing dissolved hydrogen fluoride to a fractional distillation zone in which a vaporous overhead fraction containing hydrogen fluoride and isobutane is separated from a liqlll i uid bottom/fractionwhich is, substantiallyffree from hydrogen fluoride, -.the improvement which comprises passing said vaporous. overhead. frac tion from said fractional distillation zone directly, and without intermediate g condensation thereof, into ,a liquid in.f:said pro.cess ahead of said fractional distillation zone .under-.conditions such that components ofwsaid-v vaporous, fraction are absorbed in said liquid.

7. In a process for the alkylation in -liquid phase in an alkylationzone ofgisobutane with laflowboiling olefin in4 thev presence -of` liquid; hydrogen fluoride as the catalyst,,comprisingpassingzal liquid effluent mixture from saidgalkylationzone to a separation=zonerandvtherein separating ia liquid hydrogenv iuoridefrich phase'.A and a liquid hydrocarbon-rich phase,;passing` saidy liquid hydrocarbon-rich phase containing dissolved hydrogen iiuoride to afractionaldistillation zone,

and fractionally distilling said f-material into y arv vaporous overhead fraction containing all -of'the hydrogen fluoride invia materialhhargedgto.said zone and a liquid .bottomgiraction free fromhydrogen fluoride, u the improvementwhich. comprises passing said vaporous overhead fraction from said fractional distillationzone without intermediate condensation thereof into fadmixture with liquid material in saidalkylationzone.

8. The improved process; oficlaiin, inv Which said uncondensed `vraporoiis fraction ris passed into admixture Wihfaliquidstream-:which is passing directly' intosaidgreaction zone.

9. In a process for-,reactlng'-paraiin hydrocarf ibonsin# .a reactionvzcne :in .the liquid; phase :in;the presence 4ofV a liquid f hydrogen fluoride catalyst,

Which-comprises 'vpassingpa liquid ,eluent mixture 'from said. reaction :zone vto fa, separation-zone -boiling liquid hydrocarbon 4material which .wis

free from hydrogen iiuoride, the improvement Awhich comprises :passing said' vaporous low-,boiling fraction directlyzvfrom: said-.fractional disti1la -tion v'zone without .intermediate condensation thereof into :liquid @contained in l said reaction zone.

. JOI-IN V. JOLLY.

`RVEIEERENGES- CITED The Afollowing references are of recordin the le of this patent:

UNITED 'STATES PATENTS Number Name Date `2,397,085 Boedeker iety al. l Mar. 26, 1946 413,868 v-Frey Jan. {1,194'1 ,52,414,626 YAllenvv Jan.v21, 1947 .25440,454

Vinyard; Apr. 27,1948 

5. IN A PROCESS FOR REACTING A LOW-BOILING PARAFFIN HYDROCARBON IN THE PRESENCE OF A CATALYST COMPRISING HYDROGEN FLUORIDE AND SUBSEQUENTLY DISTILLING IN A DISTILLATION ZONE A MIXTURE OF HYDROGEN FLUORIDE AND LOW-BOILING PARAFFIN HYDROCARBONS FROM A LIQUID HYDROCARBON MIXTURE CONTAINING DISSOLVED HYDROGEN FLUORIDE CHARGED TO SAID DISTILLATION ZONE FROM SAID REACTION, THE IMPROVEMENT WHICH COMPRISES SEPARATING DIRECTLY FROM SAID FRACTIONAL DISTILLATION ZONE A VAPOROUS LOW-BOILING FRACTION CONTAINING A LOW-BOILING PARAFFIN HYDROCARBON AND HYDROGEN FLUORIDE, PASSING SAID VAPOROUS FRACTION WITHOUT INTERMEDIATE CONDENSATION THEREOF DIRECTLY INTO A LIQUID HYDROCARBON-HYDROGEN FLUORIDE MIXTURE , AND PASSING A HYDROCARBON STREAM FROM SAID HYDROCARBON-HYDROGEN FLUORIDE MIXTURE TO SAID DISTILLATION ZONE AS SAID CHARGED MIXTURE. 